Rotary hydraulic machines

ABSTRACT

A radial piston hydraulic motor has a cam ring which is slidable transversely of the axis of the rotor so as to vary the eccentricity of the ring with respect to the rotor axis. The ring is engaged by a piston which is biased by a spring to urge the ring to a position of maximum eccentricity. The piston is responsive to an increase in centrifugal pressure adjacent the ring to overcome the spring and reduce the eccentricity. For a given flow the motor speed tends always to increase, resulting in high starting torque and low running torque.

United States Patent Freeman Sept. 18, 1973 ROTARY HYDRAULIC MACHINES 3,650,180 3/1972 Gantschwigg.... 91/488 3,056,357 10/1962 Bohnhofi 1 91/475 1751 u Freeman 3,518,919 7/1970 Freeman 91/475 England [73] Assignee: Joseph Lucas (Industries) Limited, P i E i r willi m L. Freeh Birmingham, England AttorneyHolman & Stern [22] Filed: Dec. 10, 1971 [21] Appl. No.: 206,757 ABSTRACT A radial piston hydraulic motor has a cam ring which 30 Foreign Application priority Dta is slidable transversely of the axis of the rotor so as to Dec 18 1970 Great Britain 60 179/70 vary the eccentricity of the ring with respect to the rotor axis. The ring is engaged by a piston which is bi- [52] U 8 CI 91/475 91/497 ased by a spring to urge the ring to a position of maxi- [511 Folb 13/06 mum eccentricity. The piston is responsive to an in- [58] 491 497 crease in centrifugal pressure adjacent the ring to overcome the spring and reduce the eccentricity. For a [56] References Cited given flow the motor speed tends always to increase, resulting in high starting torque and low running UNITED STATES PATENTS torque 2,518,578 8/1950 Tomlinson 91/475 2,646,754 7/1953 Overbeke 91/475 5 Claims, 3 Drawing Figures E 7 E2 730 \1 1O 9 PATENTED SEPI 8 I973 SHEET 2 OF 3 24 l 225 I7 l3 3 C) FIGZ.

PATENTEDSEPIBIQB 3758.899

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l2 l3 ?4 E6 FIGS.

ROTARY HYDRAULIC MACHINES This invention relates to rotary hydraulic motors and has as an object to provide such a motor in a convenient form.

According to the invention a hydraulic motor comprises a casing, a rotor supported for rotation in the casing, a plurality of radial bores in the rotor, a plurality of pistons slidable in the bores, a plurality of ports in the casing with which ports said bores successively, in use, communicate, an annular cam element rotatably mounted in the casing and surrounding the rotor, said pistons engaging an inner face of said cam element, means supporting said cam element in the casing for movement in a direction transverse to the rotor axis so as to vary eccentricity of the cam element with respect to the rotor, biasing means urging the cam element towards a position of maximum eccentricity and a piston movable in response to an increase in pressure within the casing to oppose the biasing means, the arrangement being such that said piston element is sensitive to a pressure rise which occurs in the casing as a result of a body of liquid with the casing being caused to rotate with the rotor.

A motor according to the invention will now be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 is an axial section through a motor,

FIG. 2 is a section on line 2-2 in FIG. 1, and

FIG. 3 is a section on line 3-3 in FIG. 1 of a part of the motor.

The motor has a casing formed of two parts 11, 12. Part 12 is shown in greater detail in FIG. 3 and includes a pintle 13 which extends internally of the casing 10 and supports a rotor 14. The rotor 14 includes an output shaft 14a and has six equi-spaced radial bores 15 within which pistons 16 are slidable. A cam ring 17 surrounds the rotor 14, the outer ends of the pistons 16 being engageable with the inner surface of the ring 17.

Cam ring 17 is carried by a pair of axially spaced ball bearings assemblies 18, 19 which are in turn respectively mounted on a pair of support rings 20, 21 which are slidable within the casing 10. A cylindrical member 22 which is formed with through holes 30 engages the outer edges of the support rings 20, 21 and is in turn engaged by a spring-loaded plunger 23 which is mounted in the casing part 11 and which biases the cam ring 17 towards a position of maximum eccentricity with respect to the rotor 14.

The pintle 13 is formed on opposite sides with ports 24, 25 with which, in use, the bores 15 successively communicate. Port 24 communicates via a passage 26 with an inlet 27 for the motor. Port 25 communicates via a pair of passages 28 and the interior of the casing 10 with an outlet 29 for the motor.

In use a fluid under pressure is supplied to inlet 27 and drives the motor in a known manner, the fluid being discharged via outlet 29. As is known in motors of the type described, the reaction of piston 15 against ring 17 tends to move the latter to a position of minimum eccentricity with respect to the rotor 14. Fluid within the cylindrical member 22 is urged to rotate by interaction with the rotor 14, the projecting ends of the pistons 16 and the cam ring 17. There is thus provided, owing to centrifugal force, a pressure gradient within the rotating fluid the pressure increasing with increasing radial distance from the axis of rotor 14. The higher pressure adjacent the wall of the member 22 is transferred via the holes 30 to urge the plunger 23 against its spring, allowing the motor stroke to be reduced by piston reaction as aforesaid. The centrifugal pressure component increases with increasing motor speed so that, for a given rate of fluid supply to the inlet 27 the speed of the motor will tend continually to increase, being limited by the external load applied. The motor will thus have a high starting torque and a low running torque. The motor is particularly applicable for starting and running up a rotating machine having a high moment of inertia.

1 claim:

1. An hydraulic motor comprising a casing, a rotor supported for rotation in the casing, a plurality of radial bores in the rotor, a plurality of pistons slidable in the bores, a plurality of ports in the casing with which ports said bores successively, in use, communicate, an annular cam element rotatably mounted in the casing and surrounding the rotor, said pistons engaging an inner face of said cam element, means supporting said cam element in the casing for movement in a direction transverse to the rotor axis so as to vary eccentricity of the cam element with respect to the rotor, biasing means urging the cam element towards a position of maximum eccentricity and a piston element movable to oppose the biasing means, said piston element being responsive to the pressure in a zone within the casing wherein a pressure rise occurs as a result of a body of liquid within the casing being caused to rotate with the rotor.

2. An hydraulic motor as claimed in claim 1 in which there is a pintle within the casing upon which said rotor is rotatably mounted and in which said ports are formed.

3. An hydraulic motor as claimed in claim 1 in which said biasing means comprises a spring acting upon said piston means which in turn acts upon the cam element.

4. An hydraulic motor as claimed in claim 2 in which said cam element supporting means comprises a cylindrical member mounted in the casing for sliding movement in said transverse direction and bearings rotatably mounting the cam element on said cylindrical member, said piston means acting on the cam element through the intermediary of said cylindrical member.

5. A hydraulic motor as claimed in claim 4 in which said cylindrical member is formed with a plurality of through holes whereby the pressure at the periphery of a rotating body of liquid within said member is communicated to a space within the casing surrounding said cylindrical member to act upon said piston means. t 8! t 

1. An hydraulic motor comprising a casing, a rotor supported for rotation in the casing, a plurality of radial bores in the rotor, a plurality of pistons slidable in the bores, a plurality of ports in the casing with which ports said bores successively, in use, communicate, an annular cam element rotatably mounted in the casing and surrounding the rotor, said pistons engaging an inner face of said cam element, means supporting said cam element in the casing for movement in a direction transverse to the rotor axis so as to vary eccentricity of the cam element with respect to the rotor, biasing means urging the cam element towards a position of maximum eccentricity and a piston element movable to oppose the biasing means, said piston element being responsive to the pressure in a zone within the casing wherein a pressure rise occurs as a result of a body of liquid within the casing being caused to rotate with the rotor.
 2. An hydraulic motor as claimed in claim 1 in which there is a pintle within the casing upon which said rotor is rotatably mounted and in which said ports are formed.
 3. An hydraulic motor as claimed in claim 1 in which said biasing means comprises a spring acting upon said piston means which in turn acts upon the cam element.
 4. An hydraulic motor as claimed in claim 2 in which said cam element supporting means comprises a cylindrical member mounted in the casing for sliding movement in said transverse direction and bearings rotatably mounting the cam element on said cylindrical member, said piston means acting on the cam element through the intermediary of said cylindrical member.
 5. A hydraulic motor as claimed in claim 4 in which said cylindrical member is formed with a plurality of through holes whereby the pressure at the periphery of a rotating body of liquid within said member is communicated to a space within the casing surrounding said cylindrical member to act upon said piston means. 